In a mobile network, when a user is using a network outside the home network, the user is said to be roaming. Any media sent from the user's mobile node in a visited network is sent via a visited domain gateway to a home domain gateway. The home domain gateway is located in the user's home network. The media is then passed to a network node, a so called corresponding node, for onward transmission or as the final destination of the media.
It may however be very inefficient to route all data traffic via the home network, particularly when a user is attached to a visited network. The term “local breakout (LBO)” (or sometimes also referred to as “route optimization”) is used to refer to a situation when traffic from a mobile node (MN) in a visited network is not routed via the user's home network, but is instead routed in a different way. LBO could shorten the end-to-end route and reduce the load on the home network. See WO 2007/104324 A1 for an example of local breakout.
LBO relies upon that the MN is provided with at least two IP addresses, a Local Home Address (LHoA) that is managed by the visited network and used for the local breakout and a Global Home Address (GHoA) that is managed by the home network and used for global mobility. These IP addresses can be used by the MN as the situation or policy demands, however, it is sometimes not desired to use two IP addresses since this may cause some operational costs for the MN, e.g. it is not always clear which IP address can be used and for what purpose.
If only one IP address is to be used for the MN this IP address should be the GHoA. But by using only GHoA it would be impossible to perform a local breakout session since that would require that the MN was provided with an LHoA.